The present invention relates to a device for directly monitoring, assessing and managing the useful capacity and health of batteries.
The current interest and surge in both emission-free electric vehicles communications and information technology has fuelled research and development in not only these fields but those which support them as well. One field in which research and development has increased is battery technology. Current communications devices, such as cellular telephones and PCS (Personal Communication System) units all require rechargeable battery packs. Similarly, today""s new information devices, such as PDA""s (Personal Digital Assistants), notebook computers, and palmtops also require batteries. This has led to a unique situationxe2x80x94all of these devices need battery management systems which can not only provide the end user with an indication of the battery""s remaining life but can also condition the battery so that it will last longer. Likewise, electric transportation has a need for rechargeable batteries for hybrid and battery based propulsion systems which also require battery management systems.
Battery users currently have no accurate means for determining the useful capacity of batteries. Conventional devices measure voltage, impedance, electrolyte specific gravity or other battery characteristics, but do not provide the user with direct information concerning the length of time the battery will operate under load.
A battery management system which can provide a cell or module based technique to maintain and enhance the performance of the battery pack without requiring that the battery pack be disconnected from the load or from the charging system is a major unfilled requirement.
The present invention addresses these problems by providing a device for directly assessing the useful capacity of a battery while maintaining and enhancing the battery performance of a rechargeable battery such as duration of operation under load.
This objective is achieved by performing an individual assessment of each module of a battery pack. Where used in this specification, the term xe2x80x9cmodulexe2x80x9d means one or more electrochemical cells.
A further advantage of the present invention arises from its capability to rejuvenate or boost the health of a battery module of all battery chemistries, e.g. nickel/cadmium. The selectable discharge/charge sequence which is carried out in order to assess and monitor the useful capacity of the module, also serves to enhance the capacity of the module in subsequent cycles.
In a first embodiment the present invention provides a system for determining the health of a rechargeable battery pack, said battery pack consisting of plurality of battery modules, said system comprising:
a variable discharge load for discharging a battery module;
a module charger for providing a selectable charging process for a battery module;
a controller for controlling a network of switches;
a battery module sensor system for measuring a characteristic of a battery module which operates on all modules during any battery pack operation such as pack discharge or recharge; and
a network of switches controlled by the controller, said network adapted to operatively couple each module to:
the discharge load;
the module charger; and
the module sensor system,
an expert system for controlling the controller, said expert system receiving an output of the module sensor system,
means for outputting said characterization wherein
said controller discharges and recharges each individual battery module by connecting said battery module to either the discharge load or the module charger using said network of switches; and
the expert system determines the useful capacity and characterizes the health of each module based on said characteristic of each module.
In a second embodiment the present invention provides a rechargeable battery pack having a system for determining a useful capacity of said pack, said pack comprising:
a discharge load for discharging one of said battery modules;
a module charger for charging one of said battery modules;
a controller for controlling a network of switches;
a battery module sensor for measuring a characteristic of a battery module which operates at all times of battery pack use; and
a network of switches controlled by the controller, said network being capable of operatively coupling each module to:
the discharge load;
the module charger; and
the module sensor,
an expert system for controlling the controller, said expert system receiving an output of the module sensor,
means for outputting said characteristic, wherein
said controller discharges and recharges each individual battery module by connecting said battery module to either the discharge load or the module charger using said network of switches; and
the expert system determines the useful capacity of each module based on said characteristic of each module.
In a third embodiment the present invention provides a method for determining the health of a battery pack composed of a plurality of battery modules, said method comprising:
a) selecting a battery module to be tested;
b) electrically isolating the selected module to be tested using a network of switches;
c) coupling the selected battery module to:
a discharge load;
at least one module sensor;
d) performing at least one test which determines a useful capacity of the selected battery module based on predetermined criteria;
e) discharging the selected battery module;
f) coupling the selected battery module to a module charger; and
g) recharging the selected battery module.
The invention may be used in conjunction with any device or system which is battery-powered, or which uses a battery pack as an alternative or back-up power source, such as mobile electronic equipment battery packs used in cellular telephones, computers, camcorders; computers; telecommunication or station batteries; and portable test equipment.